Process of treating zinc waste



jected to a secondbrealring action er-grind- I ,vand'for t-lnspurpose 1 preferably passordinarily co= Patented Dec. 7, 1926.

arent @RELCE.

was n vI ormaoa o arthenware seesaw-smlmoca s a remains new new- My invention relates toa processot treating zinc aste, for recoverin'gzinc materials, I

which are suitable for use inthe manufacture of lithoponawhile the same may be used for otherpurposes. v

An important object of tlIQdII VGIItlQH'lStO provide a character, for obtaining zinc -material s,-hava low-content ofchlorides.

In the Manufacture of lithoponezinc materials. such as zincash, zinc skimmi-ngsfrom galvanizing processes, zinc residues from vat Wastes, andzinc residues i-roin other indusoyed. These z nc materials- -tries,'are gain a considerable amountof chlorides. i'he chloride contentin-sueh mat ials lias'-hee11'-i"'ouncl-to be injurious to the lithopone produced, -inasinuch as the presenc e of: the same causes the lithopone t'o-discolor, when exposed-to light.

The nine inaterialshereinhetore referred to, ordinarily contain .1 (one-tenth) per cent tot} or 7 (six or seven) 'percentof'chloride. I have taining more than .1 (one-tenth) per cent of chloride impart injurious properties to the lithopone, as above stated.

Uertain zinc Waste, such as zinc ash, zinc skinnnings from the galvanizing process, zinc residue from vat Wastes, and zinc residues from other industries, contain from {thirty-live) to 85(eighty five) percent of zinc, as metallic zinc,zino oxid, zinc chloride, zinc sulphate, etc., or a-mixture ofthem all. The remaining portion of the zinc Waste comprises impurities. such as chlorides, salammoniac, irOn Sulphites or organic material.

My process comprises first orking this zincwaste or zinc materials-up tea-proper ohrsical condition, for subsequent treatment. o

. e material ordinarily occurs in large umps or the l 1l;e, ,and it IS fiTSh -PR S SGClE thiis passing through the screen isno'w solopro1ess lot the above mentioned 7 discovered that zinc materials conon, of an inch or an inch and a is half 1116511,.211'1 the large lumps of metallic are caught uponthe screen and thus separated from themater-ial. *The material Serial No 553,056.

suitable n ill to crush ,the same. The material is-preferahly crushedto at-fineness so that it willpass through a 40. (tortyimesh seen. Thezincmetallicsare caught upon the top er this vscreenand thus separated out from the material passing through the The line 1 i rial Tthus. screened is over a me etic s'egarator, which elnninatesany small particles of iron, that niav have passed through the screens. The material may he niechanically- Worked up .in different Ways, and the invention is not restricte'dto the-precise mates. stated. The material inay loe handled in Wet Way, 1 and c meta -ics.removedhylevigation. The material, thus mechanically treated is r w subjected to .the laction of sulphuric s he material is therefore introduced into isui tahle nixer, and is there treated with strong sulphuric acid. Theproportionsoof the sulphuric: acid and t e Zinc material will vary. depehdingnpon the n ture of thelzinc material, and it is {ten ocessary, to obtain .satisfaStory-ire- -sults,-to properly vary tllfiitlllOT-illllfif acid and zinc rnaterials, as inay he determined by e; erience. f tter considerable,experimen-cation, to secure the niaxiinurn. eliminationof chlorides .ior ahigh .grade ,Zinc ash containing 80 (eighty) .percent-zinc ,and 5 (live) per centchlorides, I treatBQO pounds of zinc materialwithGOG-pounds or" strong sulphuric acid. The invention :is of. course 5 in no sense restricted to these..precisepro- :portions, as the may'nhe .varieid, 7 as indicated.

The chemical reaction which takes place duringthis treatment with sulphuric acid serves to eliminate substantially: 90 (ninety) oer cent-ofthe chlorides present;, in the, zinc material. l mixture. of TFZD,":'ZIIO, ZnEll and gNH Cl is employed plus.sufficientH 89 -to .,QOiilbins-"" 511 the chlorides .present,;;hi 1t not suilim it-to: cozno etely coinhi -e. th all of the: Zn present. a result of this mixture,

Zn, and ZnSO, plus' HJI,(NI1;,),SQ, plus 11 0 is obtained. The 'H O and' 'the HCL are volatilized "The heatofthe reaction causes a considerable riseintemperature from .ahout to 180 11 *Ninetvpercentof the mole. tiles contai. ed .Withinthe material, such as hg drochlori c acid and. alninoniunichloride L are thus volatilized and; driven off-:frcm the I material. 5 I have: found that; it is .not necessary to add sufficient sulphuric acid to completely combine with all of the zinc present, but the addition of an amount of acid not sufficient to combine with all of the zinc present, will eliminate at least ninety per cent of the chlorides at this step in the process, and thus reduce the chloride content of the zinc material from 6 (six) per cent to approximately .5 (five-tenths) per cent.

The material thus treated and containing .5 (five-tenths) per cent of chloride, still possesses ,too high a chloride content, to be successfully used in making a high class lith opone. l have found that in order to reduce the remaining chloride content in the material, so that the same will be within the limits of .05 (five-hundredths) to .1 (one-tenth) per cent. that it is necessary to subject the treated material to a roasting operation.

The material in the mixer, after it has had sufficient time to react with the sulphuric acid, is in the form of a powder. This powder is dropped from the mixer into a suitable hopper, from which it is fed to the roaster. l/Vhile any suitable form of roaster may be used, I prefer to employ a rotary furnace, while an ordinary hand grate furnace is also suitable. On account of economy in labor and fuel, the rotary type of furnace is desirable. The material is now passed into the rotary furnace wherein it is subjected to a temperature varying from 500 (five hundred) degrees F. to 2000 (two thousand) degrees F., depending somewhat upon the nature of the material being treated. As a matter of fact, after considerable experimentation, I have found that the temperature may be widely varied. The best method for heating the roaster or rotary furnace, I have found, to be by a counter heat, the heat traveling longitudinally of the furnace in an opposite direction to the longitudinal travel of the material. It is preferred to use either oil or gas, for fuel, atomizing with air, so that at all times, an oxidizing atmosphere may be obtained, which has been found advantageous to the successful practice of the process.

The effect of heat upon the treated material is to partly break down some of the sulphates present, which in turn attack the small amount of the chlorides remaining, and these chlorides, due to the temperatures, are volatilized and driven 01f from the material. I have found an oxidizing atmosphere desirable, because owing to the presence of organic material and of particles of metallic zinc, there is a tendency to reduce the sulphates to free sulphur or sulphides, which results in a considerable loss of sulphur, and a product that is not very satisfactory for lithopone manufacture. The finished material as it leaves the roaster or rotary furnace, will vary somewhat in chemical composition, depending upon the amount of acid used, the original zinc content of the material, and certain impurities which cannot be eliminated by the process. The sulphate content of the finished material will, in some instances, vary between the limits of 10 (ten) to 45 (forty-five) per cent depending upon the character of the Zinc waste treated, and is a valuable addition to the treated material, because it can be used with zinc in ii lithopone manufacture. The chloride content will be reduced from say a maximum content of 6 (six) per cent in the original material to from .05 (five hundredths) per cent to .1 (one-tenth). This material is satisfactory for zinc crude, used in the manufacture of a high grade lithopone.

The zinc material may occur in such form, so as to be free from lumps or metallic zinc particles, so that the mechanical separation may be dispensed with.

It is to be understood that the form of my invention herewith shown and described is to be taken as a preferred example of the same, and that various changes may be resorted to in the order of the steps of the process, and that chemical equlvalents may be employed without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. The process of treating zinc waste con taining a high chloride content to lower such content, which comprises mechanically separating out the metallic zinc, subjecting the material thus treated to the action of sulphuric acid to remove the greater portion of the chloride content, and then roasting the material to volatilize out further of the remaining chloride content.

2. The method of treating zinc waste for obtaining a material for use in the production of lithopone, said material containing a. major portion of zinc material having a low chloride content, which comprises subjecting the zinc waste to the action of heat at approximately 2000 F. in the presence of an oxidizing atmosphere whereby the major portion of the chloride content is volatilized out, and recovering the zinc material having a low chloride content.

3. The process of treating zinc waste containing a high chloride content to lower the same, which consists in breaking the material up into relatively large lumps, screening the material for separating out the metallic zinc lumps, subjecting the material to a grinding operation to finely divide the same, screening the finely divided material to separate out metallic zinc particles, separating out the iron particles in the material, subjecting the material to the action of sulphuric acid to remove the greater portion of the chloride content, and roasting material thus treated to volatilize out lowler of the remaining chloride content. l. The method of treating zinc waste for ob aining a material for use in the production of lithopone, which comprises subjecting the zinc waste to the action of heat between substantially 500 F. and 2000 F. in the presence of an oxidizing atmosphere whereby the major portion of the chloride content is volatilized out and a zinc material relatively high in zinc and low in chlocontent is produced, and recovering said zinc material.

5. he process of treating zinc waste for obtain ride cont at, which comprises subjecting the zinc waste to the action of heat between substantially 500 F. and 2000 F. in the presence of an oxidizing atmosphere to produce a ZlIlC material relatively high in zinc and low in chloride material thus separate chloride material from the zinc mar. l, and recovering said zinc material. 6. The method of treating zinc waste for obtaining a material for use in the product 1 "an proof lithopone, such material a major portion of zinc mate- ..w'ring a low chloride content, which rises subjecting the zinc waste to the ction of heat upward to 2000 F. in the n esence of an oxidizing atmosphere to prozinc material relatively high in zinc and low in chloride material and thus separating the chloride material from the 7. no material, and recovering said zinc material. 7. The method of treatin zinc vat waste for obtaining a material for use in the production of a sun prooi lithopone, such material containing a major portion of zinc material having a low chloride content, which comprises subjecting the zinc waste to the action of heat between substantially 50a 0 F. to 2000 F. in the presence of an oxidizing atmosphere to produce a zinc material relatively high in zinc and having zinc material having a low chloa chloride content between .05 and .1 per cent and thus separatin the chloride content from the zinc material, and recovering said zinc material.

8. The method of treating zinc vat waste for obtaining a material for use in the production of a sun proof lithopone, such material containing a major portion of zinc material having a low chloride content, which comprises separating out the major portion of the chloride content and obtaining a material still possessing too high a chloride content, and then subjecting such material to the action of heat between approximately 500 F. to 2000 F. in the presence or an oxidizing atmosphere to produce a zinc material relatively high in zinc and having a chloride content between .05 and .l per cent and thus separating the chloride content from the zinc material, and recovering said zinc material.

9. The method of treating zinc vat waste for obtaining material for use in the production ot' a sun oroof lithophone, such material containing a major portion of zinc material having a low chloride content, which comprises mechanically separating out the metallic zinc from the zinc waste, subjecting the material thus treated to the action of sulphuric acid to separate out the major portion of the remaining chloride content and obtaining a material still possessing too high a chloride content, and then subjecting such material to the action of heat betweeen approximately 500 F to 2000 F. in the presence or" an ozzicizing atmosphere to produce a zinc material relatively high in zinc and having a chloride content betweeen .05 and .1 per cent and thus separating out the chloride content from the zinc material, and recovering said zinc material.

In testimony whereof I atfix my signature.

JOHN NEVIN POMEROY. 

